Oral immunotherapy for allergic diseases using transgenic rice seeds: current state and future prospects

Allergen-specific immunotherapy (IT) has been shown to provide clinical benefit for patients with allergic diseases. At present, subcutaneous and sublingual ITs are mainly authorized for clinical treatment. Oral administration of allergens seems to be the easiest way to achieve IT, though it has yet to be translated to the clinical setting, mainly due to the requirement of a large amount of allergens. Plants, especially rice seeds, have recently been recognized as superior allergen carriers for oral administration, because of their high productivity, stability and safety. Therefore, in order to establish clinically applicable oral IT, we have been developing transgenic rice seeds (Tg rice), in which major epitopes of cedar pollen allergens or house-dust mites (HDM) are expressed. The efficacy of this orally administered Tg rice was confirmed in murine models of allergic rhinitis and bronchial asthma. In the safety study of the Tg rice, no adverse effects on cynomolgus macaques were observed. In this review, we summarized the current state and future prospects of allergen-specific IT, focusing particularly on oral IT with allergen-expressing Tg rice.